Conventional electrocardiography is concerned with the measurement and analysis of voltage potential readings taken from a limited number of anatomically defined locations. The voltages between various locations are combined to form electrocardiograph (ECG) leads that are represented as waveforms and are compared to clinically developed criteria to diagnose or classify the state of a person's heart. One type of conventional electrocardiographic system has focused on the application of ten electrodes to a person's skin; six across the precordial or chest area of the person and one on each of the arms and legs. This type of system is typically called the standard 12-lead ECG system. The electrodes are commonly attached to the body by a conductive gel within an adhesive structure, or by a gel which is both conductive and adhesive.
More recently, electrocardiologists have been experimenting with a body surface potential mapping technique as a tool in scientific investigations and in improving clinical diagnosis of heart disease. In body surface potential mapping, a large number of electrodes are applied to a person's torso to obtain an estimate of the total body surface distribution of cardiac-generated potentials. This distribution is commonly displayed as a series of isopotential contours plotted on a map that represents the person's torso. The resultant isopotential map is then evaluated for the presence of features representing the particular cardiac characteristic of interest.
Proper electrode placement is a major concern in electrocardiography. More particularly, to allow a person's ECG data to be meaningfully compared to clinical data obtained from known populations, the electrode readings must be made at uniformly defined, anatomical locations. Proper placement poses difficulties, in part, because the electrodes must be positioned on people of different sizes. In body surface mapping, the desired electrode sites are arranged in a number of columns and rows, with some mapping systems utilizing as many as 240 body surface electrodes. Thus, proper electrode placement may be further complicated by the large number of electrodes to be attached.
In an attempt to alleviate electrode placement problems, a number of electrocardiograph electrode systems have been developed. One type of system simply uses individual electrodes whose relative positions are unconstrained by the separate and distinct conductive wires that couple the electrodes to a cable that is connected to monitoring equipment. Thus, this system allows individual positioning of the electrodes upon the subject person. A second type of system provides a number of electrodes directly attached to a cable, with differently proportioned electrode-cable sets used with different-sized bodies. Other systems implement a cable or harness whereby individual electrodes attached thereto can be selectively positioned along the cable or harness structure. In one device, the electrodes are connected with spring clips to the harness allowing individual electrodes to be slidingly positioned along the harness.
The electrode arrangements described above are generally cumbersome to use and are often relatively expensive. The time required for proper placement with the more cumbersome prior art systems can be particularly important in emergency situations or when a large number of electrodes are required, for example, to perform body surface mapping. Care must be exercised with a system utilizing a separate lead for each individual electrode so that individual electrodes do not become entangled, a problem that can increase the chance that any given electrode will be placed in the wrong position, particularly in emergency situations. If differently-sized electrode-cable sets are to be used to compensate for differences in body sizes, an electrocardiologist must have electrode-cable sets of several sizes at his or her fingertips. More important, the person charged with placement of electrodes is also required to select the proper size and accurately place the electrodes onto the body in a minimum amount of time. Even then, the electrode-cable set selected may not allow accurate electrode placement on persons between two sizes or at each end of the spectrum of average-sized bodies. Devices utilizing a scheme whereby the individual electrodes can be slidably positioned along an electrode cable or harness are disadvantageous in their bulk and complexity, and again, are not particularly well suited for body surface potential mapping because of the large number of electrodes required.
As can be seen, there is a continuing need to provide an electrode device which allows accurate and timely placement of individual electrodes on the body of a person, whether it be conventional electrocardiography or a technique utilizing body surface potential mapping, while reducing the complexity and cost of the device.